CVE-2026-40886
Argoproj Argo Workflows 3.6.5 – 3.6.19
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:HSummary
CVE-2026-40886 is a high-severity Improper Validation of Array Index (CWE-129) vulnerability in Argoproj Argo Workflows. Its CVSS base score is 7.7 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 31th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-40886 affects Argo Workflows, an open source container-native workflow engine for orchestrating parallel jobs on Kubernetes. The vulnerability exists in versions 3.6.5 through 4.0.4 due to an unchecked array index in the pod informer's podGCFromPod() function. When a workflow pod includes a malformed workflows.argoproj.io/pod-gc-strategy annotation, it triggers a controller-wide panic. This panic occurs inside an informer goroutine outside the controller's recover() scope, crashing the entire controller process.
An attacker with low privileges (PR:L) can exploit this vulnerability over the network (AV:N) with low complexity (AC:L) and no user interaction (UI:N). By creating or modifying a workflow pod with the malformed annotation, the attacker causes the controller to crash repeatedly. The "poisoned" pod persists across restarts, leading to a crash loop that halts all workflow processing across the cluster until the pod is manually deleted. The impact is high availability disruption (A:H) with a changed scope (S:C), as scored at CVSS 7.7 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H), and is associated with CWE-129 (Improper Validation of Array Index).
The GitHub security advisory (GHSA-5jv8-h7qh-rf5p) confirms the issue and states that it is fixed in Argo Workflows versions 4.0.5 and 3.7.14. Security practitioners should upgrade to these patched releases to mitigate the vulnerability and manually delete any affected pods to restore controller functionality.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-25267
Vulnerability Data
Argo Workflows is an open source container-native workflow engine for orchestrating parallel jobs on Kubernetes. From 3.6.5 to 4.0.4, an unchecked array index in the pod informer's podGCFromPod() function causes a controller-wide panic when a workflow pod carries a malformed…
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workflows.argoproj.io/pod-gc-strategy annotation. Because the panic occurs inside an informer goroutine (outside the controller's recover() scope), it crashes the entire controller process. The poisoned pod persists across restarts, causing a crash loop that halts all workflow processing until the pod is manually deleted. This vulnerability is fixed in 4.0.5 and 3.7.14.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.4.2V2.1.1V2.2.1V2.2.2
Mitigating Controls (NIST 800-53 r5) AI
Requires explicit validation of supplied indices/offsets/positions before they are used to access buffers or other indexable resources.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require input validation and bounds checking that prevent improper array indexing.
Vulnerability identification processes can discover missing index validation via scanning or reviews.
Patching and replacement can remediate instances of the weakness after discovery.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect out-of-bounds array access but does not prevent the weakness by itself.
Secure development lifecycle mandates input validation and bounds checking that directly prevents improper array indexing.
Application security requirements include validation of untrusted input used for indexing or addressing memory structures.
Secure architecture principles encourage defensive coding patterns that reduce index-related vulnerabilities.
Secure coding standards explicitly require bounds checking and validation of array indices derived from untrusted data.